1. Field of Invention
The need for effective transportation of people in urban regions throughout the world has been high and increasing for decades. Transportation by train, underground railways (metros), trolley cars and buses constitute supplementary networks of transportation in to and out from most large cities in the world. All of these categories of transportation have their advantages and drawbacks dependent on the actual situation, like the distances to cover, the amount of people in the region, the concentration of people in the region etc. In the later years it has become evident that a more personal based public transport system is demanded by people that else tend to use their private cars in urban district, with heavy traffic jams and pollution as unwanted side effects.
To meet this demand a network of rail tracks for comparatively small railway units need to be established. Such a system would comprise a comparatively high number of separate vehicles and therefore requires a very high degree of automation to make the system sufficiently reliable, safe, versatile and cost-effective.
One of the major challenges for such a system is to provide a guideway and chassis system that is simple and reliable, have low maintenance costs and where replacement of vehicles (units) is easy. The system should incorporate or allow easy switching for use in e.g. mesh type networks of guideways. The system should be reliable and safe in most weather conditions including heavy rain, snow and wind.
2. Description of the Prior Art
WO 01/56854 describes a prior art guideway and chassis system particularly intended for PRT. A chassis including main wheels, guide wheels, brakes and ramification wheels (switching wheels) mounted on a central, vertical main frame, is enclosed in a guideway system with a top slot that allows protrusion of the main frame up to a level where it may be connected to some kind of cabin (not shown) for the accommodation of passengers. This publication is mainly concerned with the ramification system, and how possible problems of snow, rain or ice on the guideway system are eliminated by its closed structure. Like some other priory known guideway and chassis systems for PRT it has the disadvantage that the central main frame that carries or supports all wheels, has to be comparatively high. Furthermore, any increase of the diameter of the main wheels is dependent on a vertical extension of the entire mainly closed structure.